Field of the Invention
The subject invention pertains to cooling system cleaning solutions. More particularly, the subject invention pertains to storage stable cleaning solutions useful for removing various deposits from cooling systems utilized in the transportation industries.
Today in the transportation industry, cooling systems provide cooling for internal combustion engines contain a number of diverse materials in order to maximize cooling efficiency. At the same time, modern cooling systems minimize weight in order to promote fuel efficiency. Radiators, water pumps, impellers and housings of aluminum have become increasingly common, however, traditional materials, particularly cast iron, steel, brass, and copper continue to be used as well.
The extreme conditions in which these materials function are ideal for the formation of a variety of corrosion products such as metal oxides, hydroxides, and carbonates, as well as for the deposition of scale, particularly when "hard" water, i.e. water containing appreciable quantities of magnesium, and/or calcium ions are used. Finally, high lead content solders used to join together cooling system components are subject to the development of solder bloom, a high volume corrosion product.
These various deposits when created, coat the surfaces of cooling system components or clog their cooling passages, particularly in radiators. To remove these deposits, cleaning solutions are commonly used. However, these cleaning systems must perform their cleaning function, often in highly alkaline environments, without, at the same time, corroding the metals of which the cooling system is constructed. Furthermore, the cleaning solutions must be storage stable in order to be successfully commercialized.
U.S. Pat. No. 2,802,733, teaches a cleaning solution containing ethylenediamine tetraacetic acid (EDTA), sodium tripolyphosphate, sodium hydrogensulfite, and mixed oleic acid esters of polyoxyethylene glycols. In U.S. Pat. No. 3,419,501 is disclosed a cleaning solution containing EDTA, a nitrate salt, and an alkali metal silicate. U.S. Pat. No. 3,492,238 discloses a cleaning solution consisting of citric acid, sodium phosphate, sodium hydroxyethyl glycine, and sufficient water to maintain the pH between 6 and 7. In U.S. Pat. No. 4,540,443 is disclosed a cleaning solution effective for removing solder bloom, containing a salt of EDTA, a salt of citric acid, and a soluble salt of nitric acid, optionally containing also an aluminum corrosion inhibitor.
These prior cleaning solutions have had the drawbacks of introducing undesirable contaminants, for example phosphates, into the environment; the ability to remove scale but not solder bloom; or the inability of maintaining hardness ions such as calcium in solution at high pH levels. Many commercial cleaners cause darkening and/or corrosion of aluminum, while others may have limited shelf life. It would be desirable to prepare a cleaning solution for cooling systems which is effective in removing all common manner of scale and corrosion, in removing solder bloom, in maintaining hardness ions in solution even in highly alkaline environments, and which does not utilize phosphates in its composition. Most desirably, such a cleaning solution concentrate should be storage stable over extended periods.